A Silicon Valley billionaire wants to visit the nearest star. So armed with a pile of cash and a little help from his friends—including physicist Stephen Hawking—entrepreneur Yuri Milner developed a project called Breakthrough Starshot, which was unveiled yesterday. Got questions about this imaginative new venture? Here’s everything you need to know.

Best visible in the southern sky, the bright blue star Alpha Centauri is really a system of three stars just over four light-years from Earth. [Photograph By Eso]

In a nanoshell, what will Breakthrough Starshot do?

The goal is to send spacecraft the size of postage stamps to Alpha Centauri, the nearest star system to Earth. Each nanocraft, or StarChip, will be packed with cameras, thrusters, and navigation and communications equipment—the kinds of things Silicon Valley is good at making tiny and sticking on chips. Once in space, the craft will be propelled by light rather than combustion, courtesy of a thin, perhaps three-foot-wide (one-meter-wide) laser sail attached to each chip.

Wait, what’s a laser sail?
The distances between the stars are so vast that for interstellar travel to be even remotely feasible, you need to accelerate a spacecraft to some sizable fraction of the speed of light. Instead of cruising through space using the gentle push of photons from the sun, as solar sails do, Starshot’s laser sail would feel the full punch of a 100-billion-watt laser array. From the ground, that laser would propel the featherweight nanocraft to 20 percent the speed of light.

That’s fast, but it still means it’ll take nearly 20 years to reach the Alpha Centauri system. The craft will then whiz by, snap a few photos, and beam them back to Earth.

What happens if the speeding nanocraft hits something along the way?
Lots of bad things can happen if a spacecraft traveling at a significant fraction of lightspeed collides with even a tiny dust grain. Well, one bad thing, really: Utter obliteration. But space is mostly empty space, and the project team thinks the chances of collision are small.

Great! So when will we see the first images?
Well, that’s hard to say. Plausible launches could happen in the next couple of decades. For now the project is only designed to do some serious thinking and tinkering. It’s a $100 million gamble, because without additional resources, Starshot is going nowhere. And ultimately, launching something like the StarChip will be a multibillion-dollar enterprise.

Why invest all these resources just to visit Alpha Centauri?
The Alpha Centauri system is just the first step in a grander vision of interstellar travel. In cosmic terms, this star system is right next door: 4.37 light-years (or 25 trillion miles) away.

Alpha Centauri is made of three stars, which means there will be plenty to look at. Of the three, a small, dim, reddish star called Proxima Centauri is the closest to Earth, at 4.24 light-years away. But the other two stars (A and B) are more like our sun and so are potentially more scientifically interesting. They orbit each other once every 80 years or so.

Are there any planets orbiting the stars in Alpha Centauri?
Possibly. In 2012, scientists announced they’d found a potentially rocky planet orbiting Alpha Centauri B, the smaller of the system’s two sunlike stars. Unfortunately, evidence for that planet now seems to have vanished, with repeated observations failing to find the original gravitational tugs that had hinted at the planet’s presence.

Can I see Alpha Centauri?
Absolutely, if you’re in the Southern Hemisphere. To the unaided eye, the system looks like a single bright bluish star, sitting in the sky next to the glittering Southern Cross. It’s the third brightest star in the sky, and a part of the constellation Centaurus. From the Northern Hemisphere, Alpha Centauri is difficult to see because it doesn’t rise very high above the horizon, but if you know where to look at the right time, you can catch a glimpse of it from as far north as southern Texas.

How will the nanocraft see Alpha Centauri?
The Starshot team still has their work cut out for them. For starters, it’s possible the images will just be a big, bright smear—after all, the StarChip will be zipping through space at ridiculous speed, covering the equivalent of the distance between Earth and sun every hour. The team has plans to develop optics capable of such high-speed imaging, but if they can’t figure it out, any probes that fly will send back some fantastic out-of-focus postcards from the stars. It’ll also be a long wait. Because nothing travels faster than the speed of light, it will take more than four years for those photos to get back here.

Bummer. Can we make things easier if we put the laser array in space?
Actually, that’s just what the plans were for the original laser sails. The concept has been around for decades, thanks to a guy named Robert Forward. Much of Forward’s early work suggested using space-based laser arrays to accelerate the spacecraft, because Earth’s atmosphere absorbs light and makes a ground-based array less efficient.
Starshot is proposing a ground-based array because sending 100-billion-watt lasers into Earth orbit could be somewhat politically problematic, in addition to being monstrously expensive. And now it’s possible to minimize the effects of Earth’s atmosphere using what’s known as adaptive optics, a system that corrects for atmospheric distortions and is already widely used by astronomers. To maximize their signal, the project is currently considering the costs of parking their array somewhere high and dry, such as the Atacama Desert in Chile.

Is all this new technology useful for anything closer to home?
Maybe! If the team can make it work, it’ll also be possible to send these nanocraft to places in the solar system, such as Enceladus, the geyser-spewing moon of Saturn, and Pluto, which would take only a day or three to reach at 20 percent the speed of light—a big gain over the nearly decade-long journey of the New Horizons spacecraft.

So do you think it’ll work?
Maybe. Possibly. You can log your predictions here in the meantime.